1. Field of the Invention
This invention describes a method, and an apparatus for practicing the method wherein acidic hydrogen concentration may be determined in a substantially non-aqueous medium. The invention also describes determining the acidic hydrogen concentration in a substantially aqueous medium wherein the hydrogen ion concentration is relatively low.
2. Description of the Art
It has been known for several years that lubricating oils, particularly those lubricating oils utilized in diesel or gasoline internal combustion engines, become contaminated. A major source of the contamination is due to the presence of acids such as sulfur or nitrogen containing acids. These acids are, of course, extremely corrosive to various engine parts and are ordinarily controlled by placing substantial amounts of metal bases in the lubricating oil. The function of the metal base in the lubricating oil is to neutralize the acids which are formed in the lubricating oil. The sulfur and nitrogen containing acids are typically formed from the oxidation of sulfur in the fuel and through nitrogen oxide formation during the combustion process. Additional acids are formed in the lubricating oil through free radical mechanisms. When the alkaline reserve (metal base) is depleted, the lubricating oil is no longer able to protect the engine parts against the corrosive effects of the various acids.
It is desirable to be able to determine the acidity of the oil at any given point in time due to the damage which occurs when acid build up is observed. The damage includes corrosivity, depletion of anti-oxidants and viscosity rise. In the case of passenger automotive vehicles, the manufacturer typically recommends changing the oil at set periods of time or after a certain mileage interval has been reached. The practice is particularly dangerous in the case of stop and go driving conditions where the acids rapidly build up due to poor engine operating conditions, e.g., short trips and a cold engine. In large diesel engines, the fleet owners typically have the oil analyzed at set periods to determine, among other items, the alkaline reserve balance in the oil. These tests are done because the large diesel engines often contain 100 liters or more of lubricating oil. Thus, a fleet owner may analyze the oil at a cost of a few dollars as opposed to the much larger cost of changing the engine oil.
In either the passenger car or the diesel fleet owner situation, the risk is present that the oil acidity will change too rapidly to be detected by either a standard interval oil change or an analysis. Thus, it is highly desirable to be able to monitor the acid build up within a lubricating oil on a substantially on-going basis. That is, if the engine operator were presented with adequate sensing means to determine the point at which the oil becomes relatively acid, then the oil may be changed at the point at which it is actually required.
As a standard pH meter is unable to operate within an oil of lubricating viscosity, it is desirable for practical means to be developed to determine the acid content in a substantially non-aqueous medium. While the amount of water in an engine oil is insufficient to allow a pH meter to operate, there is nonetheless sufficient water present to present substantially all of the acid species within the oil in a state wherein severe corrosion will result. This small amount of water within the lubricating oil also is sufficient to carry the acid species uniformly throughout the oil, thus, allowing a sensing means, to determine if available acid species are becoming more prevalent in the oil.
It is known from an article entitled "Electrically Conducting Polymers:A Review of the Electropolymerization Reaction, of the Effects of Chemical Structure on Polymer Films, and of Applications Toward Technology", authored by Waltman and Bargon in the Can. J. Chem. 64, 76(1986) that various aromatic heterocyclic compounds yield conducting polymers. An article entitled "Polyaniline": Interconversion of Metallic and Insulating Forms published in Mol. Cryst. Liq. Cryst. 1985 Vol. 12, pp. 173-180 by MacDairmid et al describes polymers which may be processed to useful species herein.
An article entitled, "Enhanced Stability of Photoelectrodes With Electro Generated Polyaniline Films", by Noufi and Nozik, at Volume 129, No. 10, Page 2261 et seq. describes obtaining polyaniline on a platinum film while further describing the electrochemical behavior of such films in aqueous and non-aqueous solutions.
It is known from McMaster et al, U.S. Pat. No. 2,122,578, issued July 5, 1938, that lubricants and greases may be analyzed to determine their state of depreciation. McMaster et al describe as materials which are typically found in a crankcase as being the oil, acidic materials, water, fuel ends, inorganic solids, asphaltenes and blow-by carbon. McMaster discloses making conductivity measurements of the oil, but does not appear to do so on the basis of an ongoing, in-use basis of the oil nor is there any recognition by McMaster of measuring the acid content of the oil in the absence of the other ionic species which would also give rise to a conductivity measurement. In other words, McMaster et al cannot tell the difference between hydrogen ion concentration from an acid and the remaining ionic components.
Bzdula, in U.S. Pat. No. 4,434,233, issued Feb. 28, 1984 discloses mixing a sample of oil with an equal weight of distilled water to dissolve the ionic contaminants present in the oil. The contaminated water is then separated and its conductivity determined. Bzdula only discloses determining all of the ionic components and not hydrogen ion concentration. It is also observed that Bzdula cannot determine the conductivity or hydrogen ion concentration on an in situ basis.
Malmros, in U.S. Pat. No. 4,444,892, issued Apr. 24, 1984, describes a semi-conductor device for determining haptens, antigens and antibodies. In U.S. Pat. No. 4,560,534, issued Dec. 24, 1984 to Kung et al, it is disclosed that polymer-catalysts transducers may be obtained which are useful for the determination of glucose in whole blood. Of course, neither of the foregoing references relate to the determination of hydrogen ion concentration per se, or such a determination in the presence of a substantially non-aqueous medium.
Japanese Kokai Tokkyo Koho, 61 44,339, published Mar. 4, 1986 as application number 84/164,190, states that a polymer impregnated with a metal or a graphite particle may be used to determine the degree of deterioration of the oil according to the change in electrical resistance of the detector. A nickel powder dispersed in chloroprene is also disclosed in the foregoing reference. A device employing copper which dissolves in sulfur containing acids present in a lubricant is described in Canadian Patent 1,206,079 issued June 17, 1986 to Rolf.
Upson et al, in U.S. Pat. No. 4,237,194, issued Dec. 2, 1980, states that coating compositions useful in forming conductive layers comprising latex and water as a continuous phase, and as a dispersed phase, hydrophobic polymer particles having associated therewith a polyaniline salt semi-conductor may be prepared. The coating compositions are stated to be useful in forming anti-static layers for photographic elements.
Narrmann et al, in U.S. Pat. Nos. 4,401,545 and 4,532,188, issued respectively Aug. 30, 1983 and July 30, 1985, discuss the preparation of pyrrole polymers or copolymers. The materials of Narrmann et al are highly conductive organic polymers.
U.S. Pat. No. 4,543,402, issued to Traynor on Sept. 24, 1985, describes the preparation of pyrrole polymers and copolymers thereof which are suitable for compacting.
It, therefore, remains a desirable goal to obtain polymers which may be utilized to determine acidic hydrogen concentration in a substantially non-aqueous medium on an on-going basis. The present invention deals with such technology.
Throughout the specification and claims, percentages and ratios are by weight, temperatures are in degrees Celsius and pressures are in KPascals gauge unless otherwise indicated. To the extent that references cited herein are applicable, they are incorporated by reference.